Trouble finder



Jan. 3; 1939. R. B. CUMMINGS I TROUBLE FINDER Filed April 6, 1956 2Sheets-Sheet 1 6 45M 700 5 C0/WECTED 70 LIME Me:

mm; I

Patented Jan. 3,1939

UNITED STATES PATENT OFFICE TROUBLE FINDER. Rodney B. Cummings, ForestGrove, Greg.

Application April 6, 1936, Serial No. 73,005

4 Claims. (Cl. 175-183) This invention relates to an improved method-for locating trouble such as accidental grounds or short circuits inalternating current light and power systems, or telephone lines, andcomprises portable equipment and its use as will hereinafter appear fromthe specification.

Heretofore, sundry methods and apparatus have been employed by repairmen for locating faults in line wires. Usually an exploring coil wasused in combination with an ordinary hand generator, the test manshifting the exploring coil from one side of the test lead to the otheror else the leads were shifted on the wires. By this invention suchshifting is not necessary and.

the generator is not' used. Instead a device hereinafter referred to asa cable tone is connected to the line wires and cooperates with theexploring coil.

The object of the invention is to provide simple and positive means forthe location of faults in circuits, principally those carrying telephoneor telegraph circuits.

A further object is the provision of apparatus, which is portable,sensitive and reliable in action for locating line troubles.

A further object of the invention is the provision of means fortemporarily connecting a telephone set to the lines.

With the foregoing and other objects in view, as will hereinafterappear, this invention comprises the constructions, combinations andarrangement of parts, hereinafter set forth as described and shown.

Inthe drawings wherein similar numerals indicate similar parts:

Figure l is a View of a pair of lines, to which the detecting andtesting device in accordance with the invention is associated.

40 Fig. 2 illustrates the method of connecting a cable tone to linewires where the wires are short circuited.

Fig. 3 illustrates a similar connection where two lines-are grounded.

45 Fig. 4 illustrates another application of the cable tone.

Fig. 5 illustrates a view of the support rod taken on line 5-5 of Fig. 1in the direction of the arrows.

50 Fig. 6 illustrates the exploring coil mounting means in the supportrod.

Fig. 7 shows a schematic arrangement of the cable tone.

Fig. 8 shows a schematic arrangement of the 55 impulse receivingapparatus.

Fig. 9 is a showing of the cable tone connected to the line.

Fig. 10 shows the support rod alone.

Fig. 11 shows the exploring coil mounting.

Fig. 12 shows a line connector. 5

In the broad aspect of the invention an oscillating current istransmitted from the cable tone through the lines to be tested and backto the cable tone. An exploring coil when shifted along the wires butout of contact therewith will pick lb up by induction a small amount ofcurrent when in the path of the current emanating from the cable tone.The exploring coil is mounted on a support rod and connects with anamplifier and a sound transmitter and constitutes the pick-up 6 device.As is readily apparent an amplified-signal will be received at thetransmitter wherever the cable tone current is-flowing, so that theoperator may easily trace the path of the current to the trouble source.20

Referring to Figure l the transmission lines it and 2 are shownconnected to a source 3 of alternating current for testing purposes,this source being hereinafter referred to as a cable tone.

Out of physical contact but inductively coupled 26 to these tested linesis an exploring coil l2 mounted on a telescoping type of support rod 8.Electrical connections from the exploring coil extend through the rod 6to a socket it, through a plug l5, line it, to an amplifier ll, throughline 30 it to a sound transmitter l9, in this case a head set beingillustrated.

The cable tone is more particularly illustrated in Fig. 7 wherein anelectromagnetic coil is connected across a D.- C. source of E. M. F. 35and vi- 35 brating contacts 33. An armature 3t actedon by the coil 36intermittently makes and breaks the contacts 33. Terminal leads ill and38 are connected across the coil 36 and are joined to the lines l and 2as shown in Fig. l. A bell 43 is connected to the terminal lead 38 andto ground at M. A blocking condenser at of 0.5 mmf. is placed acrossterminal leads Bl and 38. This condenser acts as a by-pass forundesirable high frequency currents that would tend to pass from 45 thecable tones into the lines.

In the modified form of the cable tone in Fig.

9 a wave trap comprising inductances All and M and condenser $2 isinterposed between the cable tone and lines to eliminate undesirablefrequencies from reaching the lines. The condenser may be located ateither end of the inductan'ces.

An exploring coil 52 found to produce very good results is one made froma model T-Ford ignition coil. In this instance the two secondary 58coils are connected in series. However, such exploring coil may also bemade by other methods well known in the art. The coil I2 is supported bya hollow insulating rod l3 having two longitudinally displacedelectrical contacts 22 and 23 which are connected to the wires of thecoil. Contact 22 is of larger diameter than 23 to facilitate insertioninto the support hood. In contact 22 is a bayonet pin to engage abayonet slot 5| (see Fig. 10)

The support rod comprises two tubular elements 6 and 1 preferably ofinsulation and mounted in adjustable telescoping relation by sleeves 8and 9 (see also Fig. 5). Sleeve 8 is secured at 28 to rod member 1 andslides over element 6. Sleeve 9 is similarly secured to the element 6. Aset screw in one or both sleeves 8 and 9 serves to hold elements 6 and lin fixed position.

In Fig. 6 contacts 25 and 26 are set in insulating bases as shown at Inand II respectively of the support rod 6 and electrically contact theconducting elements 22 and 23 of the exploring coil. Contact 25 has alarger diameter than contact 26 to correspond with the enlarged contacts22 and 23 or 46 and 41 of the detachable elements. Contact 25 has abayonet slot 5! to receive bayonet pins 50 for locking engagement. Thedetachable element Fig. 11 or 12 is inserted vertically then rotated forlocking movement or engagement.

Wires 20 and 2| lead from contacts 25 and 26 through openings 21 intothe tubular element 6 to contacts in socket l4 'at the lower end. Theelectrical contacts in socket l4 may each, as illustrated in Fig. 10, beconnected respectively with one of the contacts at 29 and 30 for apurpose to be later described.

Plug l5 connects the exploring coil with an amplifier device throughconductor cord IS. The exploring coil may be coupled to any emcientamplifier with as'rnany stages of amplification as desired, and may beresistance coupled or transformer coupled. The output of the amplifierfeeds into a receiver l9 such as high impedance headphones or a loudspeaker.

Fig. 8 illustrates the wiring scheme from the exploring coil to theheadphones corresponding to Fig. 1. r

In Fig. 2 the lines are shown short circuited at 4 while in Fig. 3',both lines are shown grounded.

In Fig. 4 is shown the cable tone connected to one of the lines I andthe bell connected to ground 44. This bell is thus in the tone circuitso that a lineman out' in the line somewhere may signal an attendant atthe cable tone by connecting an ordinary linemans portable telephone(magneto type) from one side of-the line to the ground; and by turningthe generator, the bell will ring if the trouble in the line is clearedor is of such a nature that a circuit can-be completed to the bellthrough ground and one side of the line. The bell used is or theordinary telephone typeand has at least the impedance of such type bellto avoid inter- Ierence with the proper operation of the tone circuit.

With the cable tone thus connected to the transmission lines the bell isconnected to ground from the side of the line I am testing, I may callin on this side of the line, even with the tone connected to signal anattendant at the oflice. This method does not tie up the circuit whenthe ,cable tone is connected.

In Fig. 10 the support rod is shown disconnected from the exploring coiland amplifier. It also illustrates better the. contacts 25 and 26, theinsulating elements I0 and II being purposely omitted forthis reason.The openings 21 for the wires from the contacts to the tube interior isalso "two spring clip electrical'contacts 3| and 32 at the ends. Aninsulating hollow support 48 extends at right angles and centrally ofspacer 45. On this support 48 are longitudinally displaced contacts 46and 41 similarly arranged and constructed at 22 and 23 in the exploringcoil unit. Wires concealed in parts 45 and 48 connect contacts 3| to 41and 32 to 46. It can be readily seen that either the line tapper or theexploring coil may be quickly mounted or dismounted from the supportrod.

Where the line tapper is applied to the support rod a telephone set wellknown in the art may be. connected with electrical contacts 29 and 30 inthe support rod and electrically connect with lines I and 2 throughspring clip contacts 3| and 32.

When trouble appears in the lines the cable tone 3 is connected with thelines and an oscillating current sent therefrom over the lines. Suchcurrent will travel in the paths shown in any of the Figures 2 to 4 and9.

The detecting equipment including the exploring coil, amplifier, speakeror headphones, and

the connections may all be carried in an automobile or other vehicle.The exploring coil may be placed any reasonable distance from the linesand moved by the vehicle along the direction of the lines. The amplifierserves to amplify considerably the signal receiver from the lines. Whenthe coil is moved along the lines a point will be reached where nosignal or a faint signal is obtained, theindication that the end of thecurrent path has been reached. At such point it will be found that thewires are short circuited, or one or both wires are grounded.

For carrying on a conversation the line tapper 30 is inserted in thesupport rod and a telephone is connected at 29 and 30.

Having thus described my invention, I claim:

1. In an inductive coupler for testing transmission lines thecombination of an exploring coil, an amplifier and signal receiver, of asupporting rod interposed between the exploring coil and amplifier, saidrod comprising two longitudinally adjustable members at least one ofwhich is hollow, means for holding the members in adjusted relation, twoinsulated contacts on one of the members adapted to detachably receive,placed contacts on said support of similar configuration but ofdissimilar cross-sectional area and connection means between eachcontact and coil within the support.

3. A support for an exploring coil comprising relatively longitudinallyadjustable rod members, adjustable clamping means thereon, insulatingcontacts at the upper end of one rod member,

there being two sets of contacts at the lower end amasos 3 therespective extension contacts and the spring contacts, said adjustablesupport including relatively longitudinally adjustable tubular members,-longitudinally spaced insulated contacts on one member to receive thoseon the extension, and

conductors extending into the tubular member from the support contacts.

RODNEY B. CUMMINGS.

